class Solution {
    public int removeDuplicates(int[] nums) {
        if(nums == null || nums.length == 0) return 0;
        int i = 0;
        for(int j = 1;j<nums.length;j++){
            if(nums[j] != nums[i]) nums[++i] = nums[j];
        }
        return i+1;
    }
}